ABSTRACT
Background and aims: The association between serum vitamin A (VA) and non-alcoholic fatty liver disease (NAFLD) has not been adequately studied. This study aimed to evaluate the association between them in different BMI groups among US adults. Methods: A cross-sectional study was performed using the 2017-2018 National Health and Nutrition Examination Survey (NHANES) datasets (N = 4.723). Linear/logistic regression, interaction effect and mediation analyses were adopted to analyze the association. Results: NAFLD tended to be more prevalent in adults in the middle and high tertiles of serum VA than in those in the low tertile of serum VA (OR [95% CI], 1.17 [0.94, 1.45] and 1.43 [1.16, 1.75]). In the sensitivity analysis, subjects in the middle or high tertile of serum VA had 10% (OR, 1.10 [0.88, 1.39] and 31% (OR, 1.31 [1.09, 1.58]) higher odds of NAFLD than those in the low tertile of serum VA. In the normal weight group, higher serum VA was associated with 125% and 333% higher odds of NAFLD in the middle and high tertiles, respectively, (OR, 2.25 [1.46, 3.48] and 4.33 [2.43, 7.69]) compared with the low tertile serum VA group. However, serum VA and NAFLD were not significantly associated with the obese group. Among different BMI groups (<30 compared with ≥30), serum triglycerides and insulin resistance mediated the association between VA and NAFLD in adults to varying degrees. Conclusions: In the weighted survey, serum VA was positively associated with the degree of NAFLD, especially in the non-obese population.
Subject(s)
Non-alcoholic Fatty Liver Disease , Adult , Humans , Cross-Sectional Studies , Nutrition Surveys , Vitamin A , Body Mass Index , Obesity , Risk FactorsABSTRACT
Background: Iodine nutrition is an important public health issue. Trends in iodine status over time among U.S. schoolchildren and adults and factors mediating changes of iodine status were examined. Methods: In this cross-sectional study of National Health and Nutrition Examination Survey (NHANES) data, we estimated trends in the U.S. population using linear regression analyses. Representative samples of U.S. children and adults were enrolled in NHANES 2001-2020. The NHANES cycles were categorized into 5 four-year periods: 2001-2004, 2005-2008, 2009-2012, 2013-2016, and 2017-2020. The final sample sizes of children and adults for analysis were 4288 and 19,661, respectively. The estimated average requirement (EAR) (based on guidelines from the Institute of Medicine), was used to estimate the prevalence rate of inadequate iodine intake. Binary logistic regression analyses were used to investigate the association between iodine status and contributing factors. Results: From 2001-2004 to 2017-2020, among children, urinary iodine concentration (UIC) decreased from 243 to 166 µg/L (ptrend = 0.0057) and prevalence of iodine intake below the EAR rose from 15.4% to 27.6%. In adults, the UIC decreased from 153 to 116 µg/L (ptrend < 0.001) and prevalence of iodine intake below the EAR rose from 15.0% to 17.9%. A higher prevalence rate of iodine intake below the EAR was observed in females compared with males (children, 24.0% vs. 16.5%, p < 0.001; adults, 20.0% vs. 11.1%, p < 0.001). Inadequate iodine intake was less frequent among non-Hispanic White and Hispanic compared with non-Hispanic Black in children and adults. Adults without thyroid problems had a higher prevalence of inadequate iodine intake than those with thyroid problems (16.0% vs. 13.0%, p = 0.001). Inadequate iodine intake was less likely in the children who "sometimes" and "often" consumed milk products compared with children who "never or rarely" consumed milk products (OR = 0.60 [CI 0.30-1.21] and OR = 0.24 [CI 0.13-0.43], respectively). The prevalence of inadequate iodine intake among adults reporting "sometimes" (OR = 0.70 [CI 0.58-0.83]) and "often" consuming milk products was lower than those who "never or rarely" consumed them (OR = 0.36 [CI 0.30-0.44]). Conclusions: In this weighted survey, the prevalence of inadequate iodine intake increased from 2001-2004 to 2017-2020 among U.S. school-age children and adults. Sex, race, thyroid problems, and a decreased intake of milk products were significantly associated with iodine intake below the EAR.